MARINE DIATOMACEA OF THE UL.M.B.C. DISTRICT. 9 
N. tenia, W.Sm. Connah’s Quay, very common. 
N. tryblionella, Hantz. Helsby Marsh, common. 
Plagiogramma (Grev.) gregorianum, Grev. Surface of 
Dee, rare. 
P. van-heurcku, Grun. Surface of Dee, rare. 
Pleurosigma (W.Sm.) estuariz, W.Sm. Surface of Dee, 
common. 
P. angulatum, W.Sm. Mostyn, very common. 
P. balticum, W.Sm. Connah’s Quay, very common. 
P. delicatulum, W.Sm. Mostyn, common. 
P. distortum, W.Sm. Connah’s Quay, common. 
P. elongatum, W.Sm. Mostyn, common. 
P. fusciole, W.Sm. Mostyn, very common. 
P. formosum, W.Sm. Bangor, rare. 
P. hippocampus, W. Sm. Connah’s Quay, very 
common. 
. litorale, W. Sm. Mostyn, rare. 
.marinum, W. Sm. Rhyl, rare. 
. prolongatum, W.Sm. Mostyn, common. 
. obscurum, W. Sm. Connah’s Quay, rare. 
. scalprum, W. Sm. Queen’s Ferry, rare. 
. strigilis, W.Sm. Bangor, rare. 
. strigosum, W. Sm. Mostyn, rare. 
. tenuissimum, Greg. Colwyn Bay, rare. 
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. transversale, Roper. Surface of Dee, rare. 
Most of the British forms of Pleurosigma have been 
found in this district. Mostyn and Connah’s Quay may 
be noted as particularly rich in this genus. 
Ehabdonema (Kutz.) arcuatum, Kutz. Holywell, rare. 
RK. minutum, Kutz. Hilbre Island, rare. 
Rhaphoneis (Khr.) amphiceros, Ehr. Connah’s Quay, 
common. Many varieties of this form are found in the 
district. 
